webpack/lib/dependencies/LoaderPlugin.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const NormalModule = require("../NormalModule");
const LazySet = require("../util/LazySet");
const LoaderDependency = require("./LoaderDependency");

/** @typedef {import("../Module")} Module */

/**
 * @callback LoadModuleCallback
 * @param {Error=} err error object
 * @param {string=} source source code
 * @param {object=} map source map
 * @param {Module=} module loaded module if successful
 */

class LoaderPlugin {
	apply(compiler) {
		compiler.hooks.compilation.tap(
			"LoaderPlugin",
			(compilation, { normalModuleFactory }) => {
				compilation.dependencyFactories.set(
					LoaderDependency,
					normalModuleFactory
				);
			}
		);

		compiler.hooks.compilation.tap("LoaderPlugin", compilation => {
			const moduleGraph = compilation.moduleGraph;
			NormalModule.getCompilationHooks(compilation).loader.tap(
				"LoaderPlugin",
				loaderContext => {
					/**
					 * @param {string} request the request string to load the module from
					 * @param {LoadModuleCallback} callback callback returning the loaded module or error
					 * @returns {void}
					 */
					loaderContext.loadModule = (request, callback) => {
						const dep = new LoaderDependency(request);
						dep.loc = {
							name: request
						};
						const factory = compilation.dependencyFactories.get(
							dep.constructor
						);
						if (factory === undefined) {
							return callback(
								new Error(
									`No module factory available for dependency type: ${dep.constructor.name}`
								)
							);
						}
						compilation.buildQueue.increaseParallelism();
						compilation.handleModuleCreation(
							{
								factory,
								dependencies: [dep],
								originModule: loaderContext._module,
								context: loaderContext.context,
								recursive: false
							},
							err => {
								compilation.buildQueue.decreaseParallelism();
								if (err) {
									return callback(err);
								}
								const referencedModule = moduleGraph.getModule(dep);
								if (!referencedModule) {
									return callback(new Error("Cannot load the module"));
								}
								const moduleSource = referencedModule.originalSource();
								if (!moduleSource) {
									throw new Error(
										"The module created for a LoaderDependency must have an original source"
									);
								}
								let source, map;
								if (moduleSource.sourceAndMap) {
									const sourceAndMap = moduleSource.sourceAndMap();
									map = sourceAndMap.map;
									source = sourceAndMap.source;
								} else {
									map = moduleSource.map();
									source = moduleSource.source();
								}
								const fileDependencies = new LazySet();
								const contextDependencies = new LazySet();
								const missingDependencies = new LazySet();
								const buildDependencies = new LazySet();
								referencedModule.addCacheDependencies(
									fileDependencies,
									contextDependencies,
									missingDependencies,
									buildDependencies
								);

								for (const d of fileDependencies) {
									loaderContext.addDependency(d);
								}
								for (const d of contextDependencies) {
									loaderContext.addContextDependency(d);
								}
								for (const d of missingDependencies) {
									loaderContext.addMissingDependency(d);
								}
								for (const d of buildDependencies) {
									loaderContext.addBuildDependency(d);
								}
								return callback(null, source, map, referencedModule);
							}
						);
					};
				}
			);
		});
	}
}
module.exports = LoaderPlugin;